I know, right?

An affirmation that you agree with or can relate to the preceding statement. It can be used whether the speaker actually knows or not, but in the latter case it usually means that the speaker can attribute the preceding statement to themselves as well.

This is a recently popular expression of agreement that carries a subtext. It is more than agreement with an idea (observation, opinion); it is a friendly assertion that the speaker has already had the same idea–as in, "yeah, I know"–but it goes further: it seeks validation for the speaker's claim of precedence, from the very person whose claim he's jumping. The subtext might be "Oh, you took my idea; you should be agreeing with ME, not vice versa."

A way to agree with someone. Saying you had that same idea in your head.

The stupidest saying in the entire world and so less cool than that's real. Also shortened to "right?" because the proles who chose to use this word and too lazy to use proper English.

It's complete agreement in what is being said.

An extremely fucking annoying expression used by everyone at school to say they are in total agreement. Usually used by dumbshits who think they are cool.

It has even become so popular that it is abbreviated "IKR" via texts and Internet, particularly Facebook.

This statement is used by dumbfucks to agree with something. Little do they know, they are asking the other person if they know. Whenever someone uses this idiotic phrase on me, I reply, "Why are you asking me?"